Enter the text here that is the new abstract information for your application. This section must be no longer than 30 lines of text. This project's primary aim is to understand how changes in the tax rate on work affect labor market participation and well-being outcomes of old-age beneficiaries. A second aim is to analyze how the estimated labor supply response varies over the business cycle and across subgroups of older workers. A third aim is to examine how the tax rate on work affects the timing of retirement benefit claims. To study these questions, the project proposes to combine exceptionally rich administrative data with variation from large institutional discontinuities and one program change that generate exogenous variation in the tax rate across individuals with very similar background characteristics.